cpp/src/arrow/util/vector.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#pragma once

#include <algorithm>
#include <utility>
#include <vector>

#include "arrow/result.h"
#include "arrow/util/algorithm.h"
#include "arrow/util/functional.h"
#include "arrow/util/logging.h"

namespace arrow {
namespace internal {

template <typename T>
std::vector<T> DeleteVectorElement(const std::vector<T>& values, size_t index) {
  DCHECK(!values.empty());
  DCHECK_LT(index, values.size());
  std::vector<T> out;
  out.reserve(values.size() - 1);
  for (size_t i = 0; i < index; ++i) {
    out.push_back(values[i]);
  }
  for (size_t i = index + 1; i < values.size(); ++i) {
    out.push_back(values[i]);
  }
  return out;
}

template <typename T>
std::vector<T> AddVectorElement(const std::vector<T>& values, size_t index,
                                T new_element) {
  DCHECK_LE(index, values.size());
  std::vector<T> out;
  out.reserve(values.size() + 1);
  for (size_t i = 0; i < index; ++i) {
    out.push_back(values[i]);
  }
  out.emplace_back(std::move(new_element));
  for (size_t i = index; i < values.size(); ++i) {
    out.push_back(values[i]);
  }
  return out;
}

template <typename T>
std::vector<T> ReplaceVectorElement(const std::vector<T>& values, size_t index,
                                    T new_element) {
  DCHECK_LE(index, values.size());
  std::vector<T> out;
  out.reserve(values.size());
  for (size_t i = 0; i < index; ++i) {
    out.push_back(values[i]);
  }
  out.emplace_back(std::move(new_element));
  for (size_t i = index + 1; i < values.size(); ++i) {
    out.push_back(values[i]);
  }
  return out;
}

template <typename T, typename Predicate>
std::vector<T> FilterVector(std::vector<T> values, Predicate&& predicate) {
  auto new_end =
      std::remove_if(values.begin(), values.end(), std::forward<Predicate>(predicate));
  values.erase(new_end, values.end());
  return values;
}

/// \brief Like MapVector, but where the function can fail.
template <typename Fn, typename From = internal::call_traits::argument_type<0, Fn>,
          typename To = typename internal::call_traits::return_type<Fn>::ValueType>
Result<std::vector<To>> MaybeMapVector(Fn&& map, const std::vector<From>& src) {
  std::vector<To> out;
  out.reserve(src.size());
  ARROW_RETURN_NOT_OK(MaybeTransform(src.begin(), src.end(), std::back_inserter(out),
                                     std::forward<Fn>(map)));
  return out;
}

template <typename Fn, typename From,
          typename To = decltype(std::declval<Fn>()(std::declval<From>()))>
std::vector<To> MapVector(Fn&& map, const std::vector<From>& source) {
  std::vector<To> out;
  out.reserve(source.size());
  std::transform(source.begin(), source.end(), std::back_inserter(out),
                 std::forward<Fn>(map));
  return out;
}

template <typename T>
std::vector<T> FlattenVectors(const std::vector<std::vector<T>>& vecs) {
  std::size_t sum = 0;
  for (const auto& vec : vecs) {
    sum += vec.size();
  }
  std::vector<T> out;
  out.reserve(sum);
  for (const auto& vec : vecs) {
    out.insert(out.end(), vec.begin(), vec.end());
  }
  return out;
}

template <typename T>
Result<std::vector<T>> UnwrapOrRaise(std::vector<Result<T>>&& results) {
  std::vector<T> out;
  out.reserve(results.size());
  auto end = std::make_move_iterator(results.end());
  for (auto it = std::make_move_iterator(results.begin()); it != end; it++) {
    if (!it->ok()) {
      return it->status();
    }
    out.push_back(it->MoveValueUnsafe());
  }
  return out;
}

}  // namespace internal
}  // namespace arrow